Apparatus for heat treating



, q 16, 1930.v R. M. HEAMES ET AL APPARATUS FOR HEAT TREATING Filed June 2, 1927 2 Sheets-Sheet 1 Sept. 16, 1930. R. M. HEAMES ET AL APPARATUS FOR HEAT mmune 2 Sheets-Shet 2 Filed June 2, 1927 MMUHQ ME lll lllllllllllll I I 1 n 1 l l l l h HH I HH H H J I l Pa tented Sept. 16, 1930 UNITE-D {STA T-ES PATENT o.rFI1c 1-l: I

" RICHARD 11. 33511158, or qRossErorN'rn, AND BIR ER'W. imnaursr Ann moth STARK, or DETROIT, MICHIGAN f arrnnarus roa u nar" TREATIIIG Application filed June 2, 1927. Serial m isses'e.

The invention relates in general to improvements in'the art of heat treating obarticles.

ects such as metallic bodies, and relates more specifically to. an improved process of and apparatus for treating relatively small metal articles such as nuts, washers,.bolts, screws or the like, by application ofheat, in order to alter certain characteristics of the said A general objector the invention is a pro- 'vide anew and useful process of heat treating a series-of metal articles in a manner which will insure uniformity in the charac-.

' teristics of the finally treated articles.

Another general object of the invention. is to provide simple, compact; durable and. highly eflicient apparatus for efiecting com-- ening, annealing. changing the chemicalanalysis; ging some other characteristic of the obje t 1 II. To provide an improved process-of au tomatically handling relatively delicate metallic articles in quantity and while in, highly heated condition, Without in any man-.

ner damaging theindividu'al articles. III. To provide an improvedprocess of eifectively carburizing or case hardening transporting asuccession of relatively small I capable of conducting the objects to be treated through a heat treating zone in the form metal alloy bodies, and especially bodies formed of steel.

IV.. To provide improved apparatus for objects through a treating zone wherein the temperatures exceed 300 F.' g -V. To provide an improved conveyor especially adapted to Withstand relatively high temperatures, for transporting objects in succession through a heat treating zone. a

' VI. To provide heat treatingapparatus of a relatively thin layer, either openly or in' confined condition, .as desired.

VII. T6 provide mechanismfor gradually of the mprovement are as.

an improved method of uni-' treating apparatus;

an d'gentlyconveying objectssuch as screws 1 andbolts in .quantity and in spaced relations to each other, toward, through and from a heat treating zone.

: VIIL-To-provide other improvements in. the art'of heat treatment and in the. details of construction and operation of heat treating; apparatus, whereby metallic bodies may be uniformly treated in quantity and at minimum cost.

. These and other objects and advantages of the improvement will beapparent from the following description.

\ I A clear conception of the various step s'of the improved process and of the details of construction andoperation of several embodimerits of apparatus adapted to commercially exploitthe said process, may be had by re ferring to the drawings accompanying and for-min a part of; this spec fication inwhich like re erencecharactersdesignate the same i orsimilar parts in the variousviews. v Fig. 1 is a side elevation of an improved hardening o r' annealing furnace for-heat treating a' succession of relatively small metallic-bodies or objects. I Fig. 2 is. a top view of he im roved hardening or annealing furnace, of, ig. 1.

Fig. 3 is an enlarged transverse section through the heating zone or chamber of theheat treatingffurnace shown'in Fig. 1.

Fig. 4' is an enlarged transverse section through the loading. portion" of the heat- Fig. 5 is an ,e'nlarged transvers e section through the heat treating apparatus, the sec-' tionbeing taken in the verticalplane of the axis of the tensioning drum.

Fig. 6 is" a fragmentary enlar ed sectional view through the;discharge end of the fur-I nace showing- .thedetailsof construction of the tensioningrolleny j Fig. 7 is a side elevation of a modified type of. heat treating furnace" especially adapted for case hardening'metallic'bodies.

Fig. 8 'is an enlarged transverse section through the heating zone or chamber "of the' heat treating furnace shown in Fig. 7.

' Fig. '9 is an enlarged fragmentary top view of the endless metal ribbon or element.

.' floor ofjthe chamber, fromthe sides of the heating chamber. 6, are fluent fuel burners comprises in general an endless conveyor ribbon or element 2 having upper and lower horizontal stretches and looped ends .which coact withdriving andtension drums 10, 11,

respectively. The loading portion ,of the upper or active stretch of the ribbon 2 is sup: ported upon a series of rollers 20 and is longitudinally movable between stationary ides 5, in front of theheatingchamber 6. oading pans 3, 4 normally Containing a su ply of the work or objects to be treated, may e provided on opposite sides of the element 2 ad jacent to the guides 5. The heating chamber 6 is of tunnel-like form and; has end -openings through which the upper stretch or run of the conveyor 2 extends for carrying work into and out of the chamber; Extending longitudinally of the heating ohamberdin' spaced relation to the floor,roof and. s1de-' walls thereof, is a refractory hearth 40 upon which the upper run of the conveyor may be supported, the hearth being supported by two longitudinally extending rows of piers 41. Extendingupwardly from the sides, of the hearth are walls 42, the purpose of which will presently appear. 'Firinginto the space 35 between the bottom of the hearth and the 9, the burners along one side wall being stag-. gered with respect to the burners along the other side wall as indicated in Figs. 2 and 3.

I By reason of thefact that theseburners are staggered as aforesaid, the-hot gases prod '23 in jected from the burners 7 tend to flow towar the opposite side wall of the heating chamber, upwardly along the 'side passages between the hearth and the chamber side walls,- and finally longitudinally of the chamber for exit through 'the end openings provided for the passage of the conveyor. This system of firing avoids initial impingement of high velocity gases against the conveyor, or on the work resting thereon, butneverthless insures thorough heating of the work by reason of the factthat the workis heated from above by the gases ,of combustion which circulateand fiow longitudinally of theheating chamber 6 in the upper portion 36 there of, and isfurther heated from below by heat which passes through the hearth and through the-conveyor'supp'orted thereoin It will be further appreciated that since the hearth is formed of ,refractory material and is relative'ly massive, it will not become unduly hot even though the bottom thereof forms the top of a-combustion chamber. On theother hand, it will serve as an accumulator of heat for-uniformly heating the conveyor throughout its width. By extending the side walls of the hearth 1 above the conveyor-supporting surface thereof, the upwardly rising gases of combustion are brou htinto relatively close proximity to the roo of the chamber 6, withthe result that as the two side streams meet in the space 36 above the hearth, they are deflected downwardly-into the trough formed.

ing chamber, and which may be connected to a chimney if desired,-but this hood may be omitted.

f The driving drum 10 is supported upon'a shaft 24 which is mounted in bearings adja-,

cent the discharge end of the heat-ing chamber 6, and which is continuouslyrotatable, by,

means of anelectric motor 8 or the like I through transmission gearing 9. A pres-. sure roller 22 carried by swinging supports 25, is resiliently urged against the element 2. adjacent to' the drum 10, by means of springs 26,.as shown in vFig. 6, and serves to maintain effective driving engagement between the drum 10 and themetal ribbon. The tension-drum 11 is rotatably supported upon a movable support or carriage 12 havmg wheels 13' cooperating with guide rails 14. The carriage 12 together with the drum 1 1, are constantly urged in a direction away from the driving drum 10, by means of a' weight 16 which is connected to the carriage 12 through chains cooperating with idler sheaves 15 as shown in Figs. 1 and 4. The lower or return stretch, of the element 2 may also be supported by means. of a guide plate order to prevent. excessive sagging thereof; i Located below the discharge-end of the conveyor ribbon or element 2, is a cooling tank 18 which may besupplied with a suitable cooling'medium such as oil or water. A final discharge conveyor specifically illustrated in 5 the form of an endless elevating screen 17 is adapted to deliver thetreated objects from thetank lfiyand may be 8 in'an obvious manner. j I

The improved heat treatingapparatusspccifically disclosed in Figs.-7 and 8, is of the driven by the motor same general construction as that shown in F gs. 1 1306 inclusive, but is additionally pro- .v1ded with means for confining the objects in a layer. of other material. such .as pulverized carbon 33, during the heating operation. The confiningmeans consists of a sec- I ondendless element or belt27. formed of metal, and supported above the conveyor element 2 by means of end drums 29 and rollers 34/ The belt 27 may be driven either posi-.

tively or by the element 2 acting through the intervening layer of material 33, and isprovided with side walls 28 for confining the material 33 as shown in Fig. 8. .The delivery end of the modified type of heat treating apparatus, is preferably provided with a screen 30 or similar means for separating the treated objects from the. confining material, the separating screen being adapted to deliver the removed objects to a coolingbasin or tank 32. and to discharge the confining material to a dischar e chute 31. The separating screen- 30' may obviously be made of any de-- sired length and so disposed to effectively accomplish its purpose, and may be either stationary or-vibratory. f v

The material employed in the formation of' the endless elements 2 and 27 is an important feature of the present invention, and must, be capable of efiectively resisting temperatures above.300 F., and preferably above 1300 F., without "destruction or corrosion. It has been found that so-calledstainless steel, that is, steel containing in excessof 15% of chromium and a relatively small quantity of carbon, will effectivelymeet said re quirements. Other alloy steels which are heat resistant at high temperatures and which arenot subject to corrosion by furnace gases, may'al'so be'used. The elements 2 and 27 are formed'of relatively'thin sheet metal in order to provide the desired flexibility at the looped ends of the conveyor, and the conveyor element 2 should preferably be provided with meansv associated with the opposite side-edges thereof, for retaining the objects thereon.

As specifically disclosedin Figs; 9 ancl 10,

the endlesslelement 2 is provided with series of integral outwardly extending projections 21 stamped out of the body of the ribbon, thus producing a ridge along each of the lonitudinal edges of the ribbon. These 'pro-i jections 21 extending upwardly from the object supporting side of the "belt 2, provide barriers which serve to retain the objects upon the belt without hindering free flexing of the metal band. By formin the projections 21 integral with the bani the cost of manufacture isreduced to a minimum, while maximum belt strength is retained. In order "to obviate ossible cracking of the metal belt due to the ormation of square cornered slots therein, the outer ends of the punched projections 21 are preferably rounded as shown in Fig. 9.

j By reason of the fact that the endless ele- ,ments 2 and 27 are thin'and flexible, the cost and difliculties ofreplacement are reduced to strip of material, it will. be readily appre v ing zone.

a minimum. Thus while the steel entering into the composition of saidelements, may be relatively moreexpens'ive, weight for weight, than a steel such as would ordinarily be suit, able for a relatively heavy jointed or articu lated conveyor, nevertheless on account of said elements being thin enough to be flex- .ible,the cbst of the steel entering into the conveyor is a minor factor. Furthermore, because of the fact that the conveyor is not an articulated affairbut is made from a fiat ciated'that-the cost of fabrication thereof, is reduced to a minimum. Aside from the simple operation of joining the ends of the strip to form an endless member, and of form- I .ing the side projections thereon, the strip 'may be used as it is produced .in the steel mills. The continuity of the surface presented by the ribbon or strip forming the conveyor, also prevents relativelyflsmall objects;

fromdo'dgin'g in or falling through openings such as may exist in a jointed or articulated conveyor, atthe unions between thesuccessive members. It will be further appreciated that replacement of the improved conveyor elements in a furnace, is a relatively simple operation on account ef, the fact that these elements are relatively light and may therefore be easily handled. Another very im-i -a minimum.

During normal operation of the apparatus disclosed in Figs. 1 to 6 inclusive, in the commercial exploitation of .theimproved process for the purpose of merely hardening aseries of relatively small metallic bodies or objects 7 in succession, the combustion chamber 'andy upper chamber portion 36 are in highly heated condition by virtue of the fuel burned in the combustion chamber, and one or both of the pans 3, 4 are supplied with the objects to be treated. The endless ribbon or element 2 is-being constantly advanced by operation drum 10, and thetensioning drum 1'1'is functioning to maintain the ribbon intaut condition. With the machine elements thus in action, an attendant removes the objects from .7 I i v of the motor 8, the gearing 9 and the driving t the pans 3, 4 and carefully arranges them in the form of a substantially continuous thin layer upon the advancing loading portion of the element 2between the guides 5. If the objects. are relatively heavy or of delicate construction, thus making them subject to injury when subjected. t'o'impact while in highly heated condition, the attendant should i A see to itthat the objects are arranged in segregated order so that impact therebetweenis avoided during delivery of the objects from the element 2 to the. cooling bath. If theobjects are light orof sturdier structure, this precaution need not be taken, although the thin layer format-ion should be maintained regardless of the'specific characteristic vof-the objects. After the objects have been thus properly loaded, they are carried through the vheating zone wherein both the element 2 and the objects resting. thereon are gradually and uniformly heated to-temperatures ranging from 800 F. to 2500 F. or higher, depending upon the specific characteristics of the work bein treated. Upon leaving the heate successive heated obj ects are deing zone is not as highly heated as in the hardcning'furnace and wherein final. cooling isefi'ected inaccordance wlth the final results desired. In some instances no final'cooling may be desired, whereas i-n'other' cases a final quench of-oil, water or other liquid-may be necessary. While the objects are likewise arranged in the fori'n'of athin'layer while passing through the annealing furnace, in order to insure uniformityin the treatment thereof,

they "need not, on account of the previous hardening, be subjected'to the same care in arranging them upon the element 2, that was required during the hardening operation.

, During normal operation of the apparatus disclosed in Figs. 7 and 8, in the commercial I exploitation ofthe improved process for the purpose of case hardening or carburizing metallicobjects, the endless element 2 jis being constantly advanced as previously described, and the belt 27 is likewise being constantly advanced about :the drums 29. .One ofthe pans 3,, 4 may be supplied with'the objects to be treated, and the other with the imbed-' ding material or carbon '33.; The operator after arranging the obj ects upon the element 2 as heretofore described, sprinkles the carbon 33 over the objects thus embedding the successive objects and'produci-ng a relatively thin strip of carbon with the objects concealed therein; This strip ofmaterial is encased between the elements 2 and 27 and the side walls 28, during its passage through the heating zone, thus permitting the applied heat to effectively case hardentheconfined :ebjects by application of heat through the carbon. The heat thus applied to the car'- burizing compound, generates gases which "are retained in contact with the objects at sufficiently hi temperature to cause the objects to absoi fthe carbon'contained in the gases,-thus effecting so-called case hardening. Upon delivery of the" carbon strip from the furnace, the separating screen upon which the'c arbon and the objects are deposited by gravity, becomes effective to segregate the ob ects from the carbon in an. obvious manner, whereupon the objects mavtbe cooled and delivered from the apparatus,

From the foregoing description it will be apparent that withthe improvedprocessand apparatus, the obj ects may be uniformly heat treated in succession for the purpose'of either hardening, annealing or otherwiseohanging' a characteristic thereof, without danger of =damag1ng the individual objects. The'modified apparatus of Figs 7 and 8 permits effective and continuous carburizing of the objects, and both forms of apparatus will obviously treat large quantities of material at relatively low cost. The improvedendless conveyor is adapted to effectively withstand the high temperatures to. which it is subjected, without deterioration, and the driving and tensioning devices function to continuously advance the metal ribbon without slippage.

lVhile the conveyor disclosed herein'consists of a single thin continuous ribbon of metal, it will be apparent that'the term endless conveyor is intended to,include any element or series of elements adapted to present an uhin: terrupted supporting surface for the objects within the heating chamber. -.The conveyor plate should however be relatively resistant to'corrosion under high temperature, and if a single plate. is used, the material must be ,sulficicntly ductile-to bend'without fracturing when flexing about relatively small supporting drums or pulleys. The entire apparatus is relatively simple and rigid in'construction, and is also extremely compact when the results accomplished are considered.

-\It should be understood that it is notdesired to limit the invention to the-exact steps of the improved process or tothe precise de tails of construction f'the apparatus herein described, for various modifications within the scope o'f the claims mayoccur to persons .skilledin the art.. v

4 It is claimed and desired to secure byLet- *ters Patent Y 1. In ,combination', means forming a movable stretch of ribbon for supporting a series of objects, means for confining the sue-w .cesslve objects upon said stretch in theform of a thin layer, and means forheatingthe said objects while thus confined.

2. Incombination,.- means. forming" a .stretch of ribbon 'for supporting objects in relatively spaced r'elation and in the form of a thin layer, means for confining the 'ob- :jects upon saidstretch, means for-subjecting the objects to gradually increasing temperatures while supported upon said stretch, and means for subsequently suddenly cooling the objects upon delivery thereof. from said 'stretch.

3. In a heat treating furnace, means forming. a heating zone, a conveyor comprising,

thin metal plate movable directly through said zone and presenting a continuous supporting surface for exposing to said; z one objects carried by said surface, and means carried by said plate-to prevent objects from rolling laterally from said conveyor. V 4. In a heat treating-furnace, means forming a heating zone, a conveyor comprising a single thin metal ribbon "movable directly through said zone and presenting a continuous supporting surface for, exposing to said zone objects resting upon and carried by said ribbon, and means movable with said ribbon to prevent objects from rolling laterally therefrom. a

5. In a heat treating furnace, the combina- 'tion ofmeans forminga heating chamber, a

.hearth in spaced relation to the floor of saidchamber, a material conveyor comprising an endless thin metallic band having its upper.

run supported on said hearth and having its lower run on the exterior and beneath the floor of said chamber, and means for heating 3 said hearth from below.

6. In a heat treating furnace, the combination of means formin an elongated heating I chamber, a fixed heart extending longitudiable along said-hearth within said-depression nally of the chamber in spaced relation to the floor, roof and side fwallsof-said chamber, and a movable hearth comprising an endless thin metallic band one run of which is supported by and. movable overthe' fixed hearth and the other of which is on the outside and and between saidj'walls, and means for circulating hot gases from beneath said hearth over said walls and alongobjects being transported by 'said conveyor. w

8. In a heat treating furnace, means form'- ing a"heating\'chamber, a hearthextending longitudinally within said chamber and 'having longitudinal refractory side walls 'forming a depression at the top of said hearth, a

conveyor-movable longitudinally Within said depression, and means for circulating hot.

gases laterally over said walls and longitudinally of said depression.-

9, In combination, means forming a oon.- tinuous support for objects to be treated,

. means for confining objects embedded within carburizing material in the form of a thin layer upon said support, means for heating said objects and material while thus confined, and means for finally separating the treated objects from the material.

10. In a heat treating furnace, means form ing a heating zone, a conveyor comprising a thin metal plate movable through said zone and presenting a continuous medial supporting surface for exposing to said zone objects resting upon and carried by said plate, and movable means at the sides of said plate for preventing obgects from leaving the carrying surface 0 said plate.

11. In a heat treating furnace, means forming a heating zone, and a conveyor comprising thin metal 31m movablethrough said zone and'presenting a-continuous supporting surface for exposing to said zone objects car- 'ried by said'surface, the opposite edges ofsaid plate being provided with upstanding integral projections, for preventing objects from rolling laterally from said conveyor.

12.. In a heat-treating furnace, means. forming loading and heating zones, a conveyor comprising a thin metal ribbon movablethroughjsai'd zones insuccession, a series of rollers providing a direct support for said ribbonat said loading zone, and a hearth providinga direct support for said ribbon at said heating zone.

13. :In' a heat treating furnace, means forming a heating chamber, an imperforate hearth spaced from the floor'of said chamber and havingupstanding refractory side walls, a. conveyor comprising a thin metal ribbon movableover said hearth between said side walls, and means .for circulating hot gases from beneath said hearthover said walls and along the upper surface of said ribbon.

14. In a heat treating furnace, means'forming a heating chamber, ahearth spaced from the floor of said chamber and having upstanding side walls, means for circulating hot gases from beneath-said-hearth over said.

walls, and a conveyor comprising. a flexible metallic belt, movable throughsald chamber above said hearth, said belt havingIupstanding integral portions at the opposite edges thereof and said sidewalls 'cooperatingwith said upstandingplate portions to protect the latter from'said hot gases. v

15. In a heat treating furnace, meansforming a heating chamber, ahearth extending throughsaid chamber and having upstanding refractory side walls dis osedlongitus dinally thereof, means for; c1reulating hot gases laterally over'said walls, conveyor comprising abeltmovable through. said f chamber above said hearthand'between said walls, and means movable with said belt; to revent objects from rolling laterally therefrom, said side walls cooperating with said last mentionedmeans to protect the latter h from said hot gases.

16. Ina heat treating. furnace, means forminganopen loading zone and a confined heating zone"contiguous w,ith said loading zone, a conveyor comprising a ribbon movable through said zones in succession, a series of rollers ,providing a direct support for. said ribbonatsa'id loading zone, and a stationaryhearth providing a direct supportfor said ribbon throughout said heating zone.

17 In a heat treating furnace, means forniing contiguous loading and heating'zones,

a periodically. interrupted support located at said loading zone', a hearth presenting a continuous supporting surface within said 'heatingzone, a conveyor comprising a ribbon movable over said support and said surface,

extending throughout said heating zone, a

conveyor comprising a continuous ribbon havlng anupper stretch movable over said support and said surface, a rotary drum coacting with said ribbon at the egress thereof from said heating zone,'a tension drum coacting with said ribbon at the ingress thereof to said loadlng zone, and means coactmg with said tension drum to maintain-said ribbon taut. while advancing over said rollers. 19. In a heat treatingfurnace, means forming an open elongated loading zone and a confined elongated heating zone contiguous with said loading zone, a conveyor comprlsing a ribbon movable longitudinally through said zone in succession, and stationary storage pans disposed along the opposite sides of said conveyor'at said loading zone. 7

20. The combination with a furnace having a heating zone, of a conveyor movable through'said zone, saidconveyor comprising a relatively stiff but.longitudinally flexible band provided along each of the longitudinal edges of its object supporting side with a barrier permitting free fi'efiing ofthe band.

21. The combination with a furnace having aheating zone, of a conveyor movable through said zone, said conveyor comprising a relatively stifl but longitudinally flexible band provided along each of the longitudinal edges of its object supporting side with a barrier permitting free flexing of the band, said barrier comprising a row of individual up right rigid fingers.

22. A conveyor for use in a heat treating furnace, comprising an endless metallic flexible sheet provided inwardly of its longitudinal edge with a series of relatively narrow slots and an upright projection at the end of each slot.

23. A conveyor for use in a heat treating furnace,-compris'ing an endless metallic flexible sheet provided inwardly of its longitudinal edge with a series of relatively narrow slots and an uprightprojeetion at the end of each slot of size the same as the adjoining slot.

24. A conveyor for use in a heat treat ng furnace, comprising an endless metallic flexible sheet provided-inwardly of its longitudinal edge with aseries of relatively narrow slots each of which at its end most remote from the edge of the sheet is arcuate, and an upright projection at the other end of each of said slot-s. Y

25. A conveyor for use in a heat; treating furnace, comprising an endless metallic flexible sheet provided inwardly of its longitudinal edge with a longtitulinal extending barrier for objects onthe conveyor, said'barrier comprising a series of relatively narrow upright projections permitting free longitudinal flexing'of the conveyor. 26. A conveyor for use in a heat treating furnace, comprising an'endlessmetallic flexible sheet-provided inwardly of its longitudinal edge with a longitudinally extending bar rier for objects on the conveyor, said barrier comprising a serles of relatively narrow upright projectlons permitting free longltudlnal flexing of the conveyor, and av series of slots in the sheet laterally alined with andconforming in size to the'adjoining"projec tions.

27. The combination with a furnace having a 1 heat-ing zone, of a conveyor movable through said zone, said conveyor comprising an endless longitudinally flexible metallic band provided along each of its longitudinal side edges with a barrier permitting free fiexing of the band while preventing objects from dropping ofi at said edges.

28. In a heat treating furnace, means forming a heating chamber, a hearth within said. chamber, means for delivering hot gases toobjects over the side edges of said hearth, and a conveyor for said objects' comprising alongitudinally flexible metallic band movable through said chamberabovesaid hearth, said 7 band being of less width than the distance between said side hearth edges andjbeingpro- 'vided along each. of its side edges with a bar'- rier permitting free longitudinal flexing of the band while preventing objects from dropping off at said edges; y

In testimony whereof, the signatures of the; inventors are affixed hereto. A

RICHARD M. HEAMES. I BIRGER W. LINDQUIST. HAROLD STARK. v 

